This disclosure relates in general to lithography systems, and more particularly, to techniques for maintaining components of a lithography system.
During the operation of a CO2 laser in a conventional extreme ultraviolet (EUV) lithography system, a radiation pulse is emitted by the CO2 laser. The radiation pulse strikes a tin droplet, and upon striking the tin droplet, the radiation pulse transforms into a radiation portion having a different wavelength that is in the EUV spectrum. Further, upon striking the droplet, the radiation pulse evaporates substantially all of the droplet. However, if the radiation pulse does not evaporate all of the droplet, then a byproduct is produced. The byproduct travels toward the reflective surface of a collector mirror, and impinges on the reflective surface. Over time, the byproduct collects on the reflective surface, and/or may damage the reflective surface.
In a conventional EUV lithography system, once a certain amount of byproduct collects on the reflective surface, or after the byproduct causes a certain amount of damage to the reflective surface, the collector mirror must be replaced. Replacement of the collector mirror can constitute up to 90% of the repair and maintenance costs of an EUV lithography system. Further, replacement of a collector mirror may take as long as four days, and the EUV lithography system is inoperable during that time. Although this preexisting approach has been generally adequate for its intended purposes, it has not been satisfactory in all respects.